Wheatstone's Electric Motor

  This is a mystery apparatus. Sandström (see reference at the bottom of the page) refers to it as a "voltage converter for the operation of Geissler tubes." The accompanying picture shows a device similar to the first or third one below, with the exception that there are two leads that are held off the base by insulating glass standoffs several cm in length. The 1896 catalogue of the Chicago Laboratory Supply and Scale Company lists the Vanderbilt and Amherst examples  as a "rotator for Geissler tubes", and prices it at $9.00 for use with tubes up to 9 inches in length and $24.00 for tubes up to 12 inches in length. The Amherst apparatus is actually marked "James W. Queen", but I have not found it in the 1867 to 1888 catalogues to which I have access. The 1886 catalogue of Curt W. Meyer of New York lists the same apparatus at $6.00, $12.00 and $24.00, depending on the size; the cut is exactly the same as the former reference. The 1925 catalogue of E. Leybold's Nachfolger of Cologne has a somewhat different cut of the apparatus, which is described as Trouvé's motor at a cost of $4.00. However, in Robert T. Lagemann's catalogue of the Garland Collection of Classic Physics Apparatus at Vanderbilt University, the apparatus at the left, below is described at "Wheatstone's motor". I can find no reference to this in biographical material about Charles Wheatstone. My files have a black and white photograph of an identical motor at Otterbein College in Ohio marked "Jesse L. Cheney" its the base. The otherwise-identical motor in the middle is at Amherst College, and has four poles.

   The ring inside which the coils rotates is presumably made of soft iron, and the commutator is arranged so that there is an increasing attraction to it by the energized coils as the gap decreases. Two of the motors have four inner protrusions on the ring and the one on the right has six. The bases have two connection for the motor windings, and two connections for the high-voltage needed to excite the Geissler coils clamped to the transverse bar on the rotating shaft.

                         Vanderbilt University                     Amherst College                          Union College

 REF: Arne Eld Sandström, "The Uppsala Cabinet of Physics", Annales Academae Regiae Scientiarum Upsaliensis, 25  5-36 (1983-1984)

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